Explosively actuated fastener driving power tools

ABSTRACT

An explosively actuated fastener driving power tool of the type comprising a piston rod slidingly mounted into the bore of a front part of the tool, said front part having stop means for the piston rod in its return motion, said front part being mounted on a rear part carrying the propelling charge, said rear part providing between the propelling charge and the rear end of the piston rod a gas expansion chamber for the combustion of said charge, said front and rear parts being adapted to occupy various axial positions with respect to each other in order to cause variations in the volume of said expansion chamber, wherein that said rear stop means are adapted to be drawn aside when the front and rear parts are disassembled.

United States Patent Brack Aug. 12, 1975 [54] EXPLOSIVELY ACTUATEDFASTENER 3,302,840 2/1967 Sekiguchi et a1. 227/10 X vDRIVING POWER TOOLSI Primary Examiner-Granville Y. Custer, Jr. [75] v Inventor. JacquesBrack, Nyon, Switzerland Attorney Agent-y or Firm Holman & Stem [731Assignee: Olin Ski AG, Zug, Switzerland I 22 Filed: Aug. 3, 1973 [571ABSTRACT Appl. No.: 385,557

DeCaro et al. 227/10 An explosively actuated fastener driving power toolof the type comprising a piston rod slidingly mounted into the bore of afront part of the tool, saidfront part having stop means for the pistonrod in its return motion, said front part being mounted on a rear partcarrying the propelling charge, said rear part providing between thepropelling charge and the rear end of the piston rod a gasexpansionchamber for the combustion of said charge, said front and rear partsbeing adapted to occupy various axial positions with respect to eachother in order to cause variations in the volume of said expansionchamber, wherein that said rear stop means areadapted to be drawn asidewhen the front and rear parts are disassembled.

7 Claims, 8 Drawing Figures PATENTEB Ausi 2191s FIG. 7

FIGS 2/. 21,

9, 8 G I F EXPLOSIVELY ACTUATED FASTENER DRIVING POWER TOOLS BACKGROUNDOF THE INVENTION The invention relates to improvements in explosivelyactuated fastener driving power tools.

Such tools comprise a pusher or piston rod, the rear end of which slidesinto an expansion chamber of the propelling charge combustion gas. Thesliding of the piston induces the penetration of the pin into thegenerally hard wall, which is to act as its support.

It can be realized that the piston rods thus subjected to the pressureand temperature of the charge combustion gases and which transmit thestress resulting from the penetration of the pin and which areeventually subjected to a substantial braking stress at the end of astroke are often deteriorated or damaged. Moreover, the cylinder intowhich they slide is often clogged by combustion residues or by dustoriginating from the wall in which the pin is embedded, or by thegreasing lubricant, etc. Therefore, it must be possible for this pistonrod to be easily disassembled so as to be changed and/or in order toclean the cylinder in which it slides.

Fastener driving power tools are known in which the piston rod can beextracted through the front end of its cylinder. These known tools havethe disadvantage which resides in the fact that the front part that canbe disassembled is fragile. Indeed, the front part is the one which issubjected to the shocks of the piston rod on the braking means and thestructure which can be disassembled at the front of the barrel does notmake it possible to impart to it a satisfactory strength.

Extraction of the piston rod by the rear part of its guiding cylinder ismade impossible by the fact that the piston rod must be stopped bythrust means upon its return rearward so as to be brought to a preciseposition in preparation for firing.

Moreover, fastener driving power tools of the preceding type are knownin which the volume of an expansion chamber can be modified throughrelative axial displacement of two parts of the tool between which isprovided the expansion chamber the relative axial displacement of thetwo parts can, for example, be realized by screwing one part onto theother. The stop means of the piston rod upon its return to a position inpreparation for firing are integral with the part of the tool which doesnot contain the propelling charge in order that the relativedisplacement of both parts of the tool will actually induce a variationin the initial volume of the expansion chamber while providing aconstant distance between the front end of the piston rod and the frontpart of the barrel.

SUMMARY OF THE INVENTION The invention relates to a power tool of thislatter type in which the stop means of the piston rod are arranged so asto provide for the extraction of said rod by the rear part of itsguiding cylinder when both parts of the tool are separated.

To this effect, the tool according to the invention is characterized inthat the stop means of the piston rod upon its return towards the rearare arranged so as to be drawn aside when both parts comprising theguiding cylinder of the piston rod are separated.

In this way, the disassembling of both parts of the tool makes itpossible to extract the piston rod through the rear, since the stopmeans of the piston rod are no longer operating to stop the piston rodwhich can then be easily extracted, for example, under the action of itsown weight.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be clearlyunderstood upon reading the following description of one example of anembodiment in reference to the appended drawing in which:

FIG. 1 is a schematic axial sectional view of an embodiment of the toolaccording to the invention, in the position of minimal volume of theexpansion chamber;

FIG. 2 is a sectional view along line IIII of FIG. 1;

FIG. 3 is a plan view of a locking member;

FIG. 4 is a front view of the member of FIG. 3;

FIG. 5 is similar to FIG. 1, but for another adjustment position;

FIG. 6 is an axial sectional view of that part of the tool containingthe piston rod this part being disassembled;

FIG. 7 is a schematic plan view of that part of the tool shown in FIG.6;

FIG. 8 is a schematic plan view of the other part of the tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the toolcomprises a front section or part 1 which acts as a guide for the bolt 2in a cylindrical bore 3 and as a guide for the piston rod 4 in a bore 5.The piston rod comprises, in the embodiment described, a truncatedshoulder 6 which can cooperate, at the end of a stroke, in case ofexcessive penetration, with a shoulder 7 of bore 5 having acorresponding shape. Shoulder 6 and 7 are shown as braking and stopmeans for the piston rod beyond its active stroke, but any other dampingor stopping device being possible. It can be seen that part 1, which canbe made to sustain substantial stresses, is very bulky and willtherefore resist forces on it quite satisfactorily.

In its rear cylindrical portion, part 1 comprises on the outside, athreading 8 providing for the screwing of a rear part 9 comprising aninternal corresponding threading 10. The piston rod 4 comprises, afterthe truncated shoulder 6, a cylindrical part 28 and, eventually, ajunction 29 and a rear cylindrical rod 11 having a small diameterco-operating with a bore 12 of part 9. Bore 12 comprises, at its endopposite to the rod 11, a propelling charge 13, which can be ignited bymeans known per se shown schematically by a firing pin 14.

Piston rod 4, upon its return to the rear by means known per se, (notshown), after the firing, abuts, through a shoulder 15, provided behindcylindrical part 28, against stop means integral with part 1. This stopmeans comprise, in the example described, two stop members in the formof balls 16 which can slide radially inside through bores 17 drilledinto the rear section of part 1, in the rear zone of bore 5. Bores 17have a diameter which is barely greater than that of balls 16 in orderto make it possible for them to slide but have a diameter which isslightly reduced at their ends so as to prevent balls 16 from leavingbores 17 while making it possible for them to project therefrompartially, the length of bores 17 being smaller than the diameter ofballs 16. Outside part 1, the internal cylindrical surface 19 of part 9which bears threading 10, closes the external ends of bores 17 so thatballs 16 are pushed back towards the internal ends of these bores andpartially project inside bore 5. Their cooperation with shoulder ofpiston rod 4 provides for the stopping of the latter upon its rearwardreturn.

It can therefore be seen that whatever the relative axial position ofparts 1 and 9 may be, the capacity L of the gun, i.e.. the distancebetween the front end ,of piston rod 4 and the front end of bore 3, isconstant. On the other hand, the initial volume of the propelling charge13 combustion gas expansion chamber varies as a function of the relativeposition of parts 1 and 9. In the position of FIG. 1, part 1 is screwedat the maximum into part 9 and abuts against the latter; the volume ofchamber 18 is minimal and therefore, the firing power is maximal. On theother hand, in the position shown in FIG. 5, the two parts are notabutting against one another and the volume of chamber 18 hasconsiderably increased: the firing power is therefore reduced. It can benoted that as soon as the rear end of rod 11 of the piston rod 4 hasleft bore 12, a part of the volume of internal bore 19 of part 2 adds onto the volume of chamber 18, which makes it'possible to obtain quitevaried adjustments. In order to avoid accidents, communicating meansfrom the inside of bore 19 to the outside through a conduit 20 can beprovided. Indeed, if parts 1 and 9 are screwed onto one another only bymeans of the first threads of their screw threads, ignition of charge 13might, as a result of the pressure introduced into bore 19, lead to theseparation of parts 1- and 9 of the tool which would be dangerous. Thejudicious arrangement of conduit 20 makes it possible to eliminate sucha risk.

The invention also provides for means for the precise positioning andlocking of parts 1 and 9 with respect to each other. These meanscomprise a ring 21 (FIGS. 1 to 5) the internal diameter of which isslightly greater than the external diameter of the rear cylindricalsection of part 1. Ring 21 comprises two diametrically opposed radialpins 22 co-operating with longitudinal grooves 23 (FIG. 2) bored intothreading 8 of part 1, and with recesses 27 provided in part 9. Ring 21is pushed back into abutment against the front end of part 9 through ahelicoidal spring 24. In order to effect the adjustment, ring 21 ispushed back towards the front against the action of spring 24 and part 1is screwed into part 9 up to the desired position. Care must be taken sothat grooves 23 face recesses 27 so that ring 21 can return into meshingengagement with part 9 under the action of spring 24 and prevent anyscrewing or unscrewing. The adjustment therefore, in this case,

is effected by screwing or unscrewing half turns. The number of pins andrecesses may be different in order to obtain an adjustment by turns,quarters of a turn, thirds of a turn, etc..

The disassembly of the tool is extremely easy. While maintaining ring 21pulled towards the front, part 1 is completely unscrewed from part 9.Part 1, which is separated, then makes it easy to extract piston rod 4thanks to the fact that the balls 16 are no longer pushed back towardsthe inside of bore 5 (FIG. 6). By placing this part 1 in a verticalposition with its front part directed upwards, the weight of piston rod4 pushes back balls 16 towards the outside of part 1 and the rod 4 fallsoutside of the part. The reassembling is easily effected in the oppositedirection.

In order to display the power adjustment, there are provided, on thefront part 1, numbers or marks 25 (FIG. 7) which may be read through awindow 26 provided opposite part 9 (FIGS. 1, 5 and 8).

The stop member which can be drawn aside for piston rod 4 can of coursebe provided by other known means, for example, a split ring with a rearconical profile producing a constriction in the ring through passage ofpart 9 and projection of the ring inside bore 5.

What I claim is:

1. An explosively actuated fastener driving tool of the type comprising,in combination: a front part and a rear part, means removably connectingsaid front and rear parts to each other, said front part including anaxial bore; a piston rod slidingly mounted in said bore; and stop meansincluding portions projected into said bore in the vicinity of said rearpart for cooperating with the rear end of the piston rod to limit itsmotion toward the rear when said rear part is connected to said frontpart, said portions of said stop means being slidable out of said borewhen said rear part is removed from said front part, said rear partproviding between a propelling charge and said rear end of the pistonrod a gas expansion chamber, said means removably connecting said frontand rear parts to each other permitting axial adjustment between saidfront and rear parts in order to cause variations in the volume of saidexpansion chamber.

2. A power tool according to claim 1 wherein the front part is threadedand screwed into a threading of the rear part.

3. A power tool according to claim 2, wherein the front part has atleast one axial groove, a ring having at least one radial catch, thering and a spring mounted on the front part, said spring urging saidring toward said rear.

4. A power tool according to claim 1, wherein said stop means includesat least one stop member slidingly mounted within a transverse boreformed in said front part, transverse bore being opened at one end intothe said axial bore of the front part and at the other end at theoutside of said front part in an area thereof which is always covered bysaid rear part when said. front and rear parts are assembled together,the maximum dimension of said stop member along the length of saidtransverse bore being greater than the length of said transverse bore.

5. A power tool according to claim 4 wherein said stop member is a ball.

6. A power tool according to claim 4, wherein the front part is providedwith marks and the rear part is provided with at least one window forthe reading of said marks.

7. A power tool according to claim 4, wherein the rear part comprisesmeans for setting'up communication between the expansion chamber and theatmosphere, said means operating when the front part is looselyconnected to the rear part. l

1. An explosively actuated fastener driving tool of the type comprising,in combination: a front part and a rear part, means removably connectingsaid front and rear parts to each other, said front part including anaxial bore; a piston rod slidingly mounted in said bore; and stop meansincluding poRtions projected into said bore in the vicinity of said rearpart for cooperating with the rear end of the piston rod to limit itsmotion toward the rear when said rear part is connected to said frontpart, said portions of said stop means being slidable out of said borewhen said rear part is removed from said front part, said rear partproviding between a propelling charge and said rear end of the pistonrod a gas expansion chamber, said means removably connecting said frontand rear parts to each other permitting axial adjustment between saidfront and rear parts in order to cause variations in the volume of saidexpansion chamber.
 2. A power tool according to claim 1 wherein thefront part is threaded and screwed into a threading of the rear part. 3.A power tool according to claim 2, wherein the front part has at leastone axial groove, a ring having at least one radial catch, the ring anda spring mounted on the front part, said spring urging said ring towardsaid rear.
 4. A power tool according to claim 1, wherein said stop meansincludes at least one stop member slidingly mounted within a transversebore formed in said front part, transverse bore being opened at one endinto the said axial bore of the front part and at the other end at theoutside of said front part in an area thereof which is always covered bysaid rear part when said front and rear parts are assembled together,the maximum dimension of said stop member along the length of saidtransverse bore being greater than the length of said transverse bore.5. A power tool according to claim 4 wherein said stop member is a ball.6. A power tool according to claim 4, wherein the front part is providedwith marks and the rear part is provided with at least one window forthe reading of said marks.
 7. A power tool according to claim 4, whereinthe rear part comprises means for setting up communication between theexpansion chamber and the atmosphere, said means operating when thefront part is loosely connected to the rear part.